Inhibition by vasodilators of noradrenaline and vasoconstrictor-mediated, but not skeletal muscle contraction-induced oxygen uptake in the perfused rat hindlimb; implications for non-shivering thermogenesis in muscle tissue.
1. The effect of noradrenaline as well as of vasopressin and angiotensin II to increase oxygen uptake and perfusion pressure by the isolated perfused rat hindlimb were completely inhibited by the vasodilators, nitroprusside (0.5 mM), nifedipine (2.5 microM) and isoprenaline (50 nM). 2. Oxygen uptake due to sciatic nerve stimulation of skeletal muscle contraction was not inhibited by 0.5 mM nitroprusside but was found to increase further that produced by a maximum dose of either noradrenaline or angiotensin II. 3. Analysis of high energy phosphates in samples of freeze-clamped hindlimb muscle showed no difference before and after vasoconstrictor addition or with muscle sampled in vivo. 4. It is concluded that norepinephrine mediated increase in oxygen uptake by the perfused rat hindlimb results from its vasoconstrictor action.
Colquhoun
E Q
EQ
Department of Biochemistry, University of Tasmania, Hobart, Australia.
Hettiarachchi
M
M
Ye
J M
JM
Rattigan
S
S
Clark
M G
MG
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D004558:Electric Stimulation; D006614:Hindlimb / Q000098:blood supply / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D009638:Norepinephrine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors*; D014665:Vasodilator Agents / Q000494:pharmacology*; D014667:Vasopressins / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D014667:Vasopressins; D000804:Angiotensin II; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D009638:Norepinephrine